THE EFFECTS OF BLEACHED AND UNBLEACHED ROSEMARY OLEORESINS ON LIGHT-SENSITIZED OXIDATION OF SOYBEAN OIL

Bleached and unbleached forms of a rosemary oleoresin (RO) in stripped and nonstripped soybean oil behave both as antioxidant and prooxidant in a light-induced oxidative system. At 0.02 and 0.05% levels, RO had the greatest antioxidant activity, while at 0.01 and 0.5% levels it h ad the highest prooxidant activity in both stripped and nonstripped so ybean oil. Treatment of both soybean oil systems with tertiary butylhy droquinone controlled light-induced oxidation of the oil better than d id the oleoresin treatments. The prooxidant activity of the 0.5% RO le vel was probably due to an excess of prooxidant components being carri ed into the oil at that level, whereas the reduced antioxidant activit y at 0.01% was probably due to the low initial level of active antioxi dant components being added to the oil.